Rear bumper of an automobile



FIG. 1 is a front elevation view of a rear bumper of an automobile, showing my new design;

FIG. 2 is a left side elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a right side elevation view thereof; and,

FIG. 5 is a top and rear perspective elevation view thereof. 

The ornamental design for a rear bumper of an automobile, as shown and described. 